This invention relates to an elastically stretchable composite sheet and a disposable wearing article using this composite sheet.
The elastically stretchable composite sheet comprising an elastically stretchable sheet and an inelastically stretchable sheet bonded together intermittently in a direction in which these sheets are stretchable is well known, for example, from Japanese Patent Application Publication No. 1987-28456A. In this composite sheet of well known art, the inelastically stretchable sheet is formed with a plurality of pleats arranged in the direction in which this sheet is stretchable.
In one practical use of such an elastically stretchable material for the wearing article, it is intended to increase a stretching stress of this material sharply as soon as it has been stretched to a certain limit of stretching. For example, the elastic member associated with a waist-opening of a pants-type disposable diaper or training pants is adjusted so that while this elastic member does not positively lace the wearer""s waist so far as no brisk movement of the wearer occurs, wearer""s waist is positively laced by the elastic member and the diaper or the pants are prevented from slipping down because the lacing effect of the elastic member sharply increases as the brisk movement of the wearer""s body further stretches the elastic member. It should be understood here that the lacing effect of the elastic member varies progressively, e.g., in two or three steps, rather than abruptly varies.
In the case of the composite sheet well known from the Japanese Patent Application Publication No. 1987-28456A, the elastically stretchable sheet is elastically stretched and at the same time the pleats of the inelastically stretchable sheet come out as the composite sheet is stretched. After the composite sheet has been stretched until the pleats completely come out, a stretching stress of the composite sheet abruptly increases since the elastically stretchable sheet must be stretched together with the inelastically stretchable sheet. While such composite sheet of well known art is certainly one of the elastically stretchable materials suitable for use in the pants-type disposable diaper, it is a problem accompanying this composite sheet that the stretching stress abruptly varies at once.
In view of the problem as has been described above, it is an object of this invention to provide the elastically composite sheet improved so that its stretching stress may be varied at least in two steps. A second object of this invention is to provide a pants-type disposable wearing article using such composite sheet to achieve an improvement such that the wearing article may be easily put on a wearer""s body and prevented from slipping down once the article has been put on the wearer""s body.
According to one aspect of this invention, there is provided an elastically stretchable composite sheet comprising a first sheet having x- and y-directions orthogonal to each other and being elastically stretchable at least in the y-direction and a second sheet being inelastically stretchable at least in the y-direction wherein the first and second sheets are bonded intermittently in the y-direction to form the composite sheet adapted to be elastically stretchable in the y-direction.
The improvement in the elastically stretchable composite sheet according to this invention is in that a third sheet being elastically stretchable in the y-direction and having a dimension in the y-direction longer than the first sheet is bonded to at least one surface of the first sheet intermittently in the y-direction so that the third sheet has a plurality of pleats formed due to a dimension by which the third sheet is longer than the first sheet in the y-direction, and the second sheet having a dimension in the y-direction longer than both the first and third sheets is bonded to the first directly or indirectly by means of the third sheet so that the second sheet has a plurality of pleats formed due to a dimension by which the second sheet is longer than the first sheet in the y-direction.
The second object set forth above is achieved, according to the other aspect of this invention, there is provided a pants-type disposable wearing article comprising a front waist region, a rear waist region and a crotch region extending between these two waist regions wherein the two waist regions are bonded together along transversely opposite side edge portions of the respective two waist regions to form a pants-type structure.
The improvement in the pants-type disposable wearing article according to this invention is in that the front and rear waist regions are at least partially formed by a composite sheet having elastic stretchability in a circumferential direction of the wearing article wherein the composite sheet comprises (1) a first sheet having elastic stretchability in the circumferential direction, (2) a third sheet having a dimension in the circumferential direction longer than the first sheet and elastic stretchability in the circumferential direction, the third sheet being bonded to the first sheet intermittently in the circumferential direction so that the third sheet has a plurality of pleats formed due to a dimension by which the third sheet is longer than the first sheet in the circumferential direction and (3) a second sheet having a dimension in the circumferential direction longer than both the first and third sheets and inelastic stretchability in the circumferential direction, the second sheet being bonded to the first directly or indirectly by means of the third sheet so that the second sheet has a plurality of pleats formed due to a dimension by which the second sheet is longer than the first sheet in the circumferential direction.